if err := c.Wait(); err == nil {
		t.Error("program unexpectedly exited successfully")
	} else {
		t.Logf("exit status: %v", err)
	}
}

// test that environment variables are de-duped.
func TestDedupEnvEcho(t *testing.T) {
	t.Parallel()

	cmd := helperCommand(t, "echoenv", "FOO")
	cmd.Env = append(cmd.Environ(), "FOO=bad", "FOO=good")
	out, err := cmd.CombinedOutput()
	if err != nil {
		t.Fatal(err)